Awesome…you will have a great time!!! Be sure to get the homemade ice cream at The Dairy which is in the student union.
Here’s a thread I started to give you some info about engineering in general http://talk.collegeconfidential.com/university-maryland-college-park/1732708-everything-you-want-to-know-about-engineering-at-maryland-p1.html
In answer to your question about merit aid, well, you need to bear in mind that it’s a public university, so there are no huge endowments like private universities. There is def some merit money though. Also, as a public state university, the majority of students do come from Maryland, but with such a large student population in general, the percentage of OOS translates to a good number.
As for nanotechnology, you might want to check out this page https://www.nanocenter.umd.edu. Not sure if your son would be interested in micro robotics…? Maryland has that as well (let me know because there are other links on this I can give you if he is interested) https://sites.google.com/site/microroboticslaboratory/